Humidifying process in electric cable insulation making



1956 s. w. PERGUNAS ETAL 2,770,565

HUMIDIFYING PROCESS IN ELECTRIC CABLE INSULATION MAKING Filed June 15,1955 Inventor s, w. PERGUNAS L. COWAN By/A %1 Attorney United StatesPatent HUMIDIFYING PROCESS IN ELECTRIC CABLE INSULATION MAKING SidneyWilfred Pergunas and Leslie Frank Cowan, London, England, assignors toInternational Standard Electric Corporation, New York, N. Y.

Application June 15, 1953, Serial No. 361,768

Claims priority, application Great Britain June 23, 1952 8' Claims. c1.1s4 2.z4

This invention relates to the manufacture of electric cables and hasparticular reference to the process of applying paper insulation toconductors for use in multiconductor telephone cables.

In the copending application, Serial No. 201,348 filed December 18,1950, there is described a process for making pairs of insulatedconductors in which two conductors are passed simultaneously with astrip of paper through a heated die, the shape of the die being suchthat the paper is folded in 8 formation around and between the two wiresthus forming an insulated pair.

As explained in that specification the strip of paper is supplied in anundried condition and the evolution of water vapour as steam facilitatesthe passage of the paper through the folding die. In addition thefolding of the paper while it is giving off its moisture in the heateddie results in an ironing action which causes the paper to be foldedround each wire in the form of a permanently shaped tube which cannotreadily be detached from the wire.

In the copending application, Serial No. 456,266 filed September 15,1954 there is described a further development of the process in whichsingle conductors are insulated. This has been found possible because ofthe unexpected firmness developed by the insulating paper after it hasbeen formed around the conductor in the heated die.

Under normal conditions with the atmospheric relative humidity about 60%it is found that the insulating paper contains about 8% by weight ofwater. However weather conditions are changeable and during and after aprolonged spell of high relative humidity the moisture content of thepaper may be found to be in excess of 8% while after a prolonged spellof very dry weather the moisture content may fall considerably and evenresult in the ironing process in the heated die being unsatisfactory.

In some climates it is possible that the relative humidity would oftenbe so low that the process could not be successfully operated. In anycase the variations in relative humidity must result in variations inthe electrical characteristics of the product.

Attention has therefore been directed to the effects of controlling themoisture content of the paper. It has been found, as would be expected,that if very dry paper is used the ironing effect is imperfect and thepaper tends to unroll on leaving the die. At the other extreme it hasbeen found that if very wet paper is used it wraps itself very closelyaround the conductor. In this case the mutual capacity between theconductors, particularly in the case of the 8 formation, is very highand possibly for many purposes excessive. The insulation is howevermechanically excellent and for some purposes this may be more importantthan low mutual capacity.

Although the process has been reasonably satisfactory with the ordinarycondition of approximately 8% humidity experiments have shown that amore satisfactory 2,770,565 Patented Nov. 13, 1956 product is obtainedif the moisture content is increased providing it is not excessive.

Several methods for dampening the paper are available. In one methodsteam jets are directed onto the paper just before it enters the formingdie. This means in effect that the paper passes through an atmospherewith a relative humidity of but the resulting moisture content of thepaper is controlled by the speed of the paper and the size of the steamjet. This method has an advantage when insulated pairs with S shapedinsulation are being formed. It has been found that the paper tends tocurl when the jet is applied so that by applying one jet to one half ofone side of the paper and a second jet to the other half of the paperand from the other side the strip of paper can be made to commence totake up the 8 formation before it enters the die.

If single conductors are to be insulated a single steam jet is appliedto the whole of one surface of the paper strip.

An alternative method of dampening the paper is to direct very finesprays of water on it, preferably one on each surface, before it entersthe die. This requires very careful control if the paper is not to bemade too wet but this method has been used successfully.

Yet a third method is provided by passing the paper strip betweenmoistened sponge rollers and this method lends itself to easy control ofthe amount of moisture applied.

A further method is to supply the paper from pads (rolls) which havebeen held in a chamber at a controlled humidity for a time sufficientlylong to ensure that the paper is uniformly humidified.

Yet another method is to pass the strip of paper through a humidifyingchamber after it is rolled off the supply pad and before it enters thedie.

The invention therefore comprises a method of insulating electricconductors by the longitudinal folding of a strip of paper in a heateddie so that it lies around the conductors, characterised in this thatthe strip of paper is subjected to a humidifying process to impart acontrolled moisture content thereto immediately before it is supplied tothe heated folding die.

As the paper supplied to the die according to this invention may have ahigher moisture content than that previously used it may be foundnecessary to dry the insulated conductor as it leaves the folding die.This can be done by passing the insulated conductors through a shortsizing die maintained at a temperature above that of the folding die.

Embodiments of the invention will now be described with reference to theaccompanying drawing in which:

Fig. 1 illustrates the dampening of the paper by means of steam jets;

Fig. 2 illustrates the dampening of the paper by means of a water sprayand,

Fig. 3 illustrates the dampening of the paper by passing it betweenmoistened sponge rollers.

In Figure 1 there is shown a forming die such as is described andillustrated in the aforesaid copending application Serial No. 201,348which is employed to form insulated pairs with the insulating paperwrapped around the two conductors in S formation. It can be seen thatthe two conductors 11, are passed into the die 2 simultaneously with astrip of paper 3 which is then folded within the die into 8 formationaround and between the conductors. In the present invention steam jets 45 are directed against the paper strip 3. The steam is supplied throughthe inlet 6. As shown steam jet 4 is directed against one half of theupper surface of the strip and jet 5 against one half of the lowersurface. Apart from the fact that these jets increase the moisturecontent of the paper strip they produce a tendency in the strip to curlin the desired directions and therefore facilitate the formingoperation. The speed of the paper strip and the emission of steam fromthe jets must be so controlled as to result in the desiredhumidification of the paper strip which is determined by the desiredresult.

In Figure 2 there is shown a forming die such as is described in theaforesaid copending application Serial No. 456,266 in which a strip ofpaper is wrapped around a single wire to form an insulated conductor.The conductor 7 is passed into the die 8 together with a strip of paper9. As shown in the figure a jet of compressed air from an orifice 10 isblown against the upper end of a tube 11 the lower end of which isimmersed in a water container 12. This water spray is directed againstone side only of the paper strip 9 and increases the moisture content ofthe paper, and also induces a tendency for the paper strip to curl inthe desired direction. Although a water spray is illustrated in Fig. 2the same result can equally be achieved by means of a single steam jetsuch as is illustrated in Fig. 1.

In Fig. 3 a third process for increasing the moisture content of thepaper strip is illustrated. A paper strip 13 is passed between twosponge rollers 14, the lower one of which dips into a water bath 15 andthen led to the die 16. This die, which is only representedschematically can be either of the kind illustrated in Fig. 1 designedto form S shaped insulation or of the kind illustrated in Fig. 2designed to wrap the strip of paper around a single conductor.

While the principles of the invention have been described above inconnection with specific embodiments, and particular modificationsthereof, it is to be clearly understood that this description is madeonly by way of example and not as a limitation on the scope of theinvention.

What we claim is:

1. A method of insulating electric conductors by the longitudinalfolding of a strip of paper in a heated die so that it lies around theconductors, characterized in that the strip of paper is subjecteddirectly to a jet of steam to impart a controlled moisture contentthereto immediately before it is supplied to the heated folding die.

2. A method according to claim 1 in which a first steam jet is appliedto one half of one surface of the paper strip and a second steam jet isapplied to the opposite half of the other surface of the paper strip.

3. A method of insulating an electric conductor by applying a strip ofpaper therearound, comprising subjecting substantially the completepaper strip to a humidifying process to impart a controlled moisturecontent thereto, longitudinally folding said moistened strip of paperaround said conductor, and heating said paper sufliciently so that thereaction of the heat and moisture sets the paper in its folded position.

4. A method according to claim 3 in which the humidifying processcomprises the application of a water spray to at least one side of thepaper strip.

5. A method according to claim 4 in which a first Water spray is appliedto one half of one surface of the paper strip and a second water sprayis applied to the opposite half of the other surface of the paper strip.

6. A method according to claim 3 in which the humidifying processcomprises passing the paper strip between two rollers one of which ismoistened by being partially immersed in a water bath.

7. A method according to claim 3 in which the humidifying processcomprises the use of rolls of paper strip which have been held in ahumidifying chamber at a controlled humidity for such time as to ensurethat the paper is uniformly humidified.

8. A method according to claim 3 in which the paper strip is passedthrough a humidifying chamber maintained at a controlled humidityimmediately before it is passed to the folding die.

References Cited in the file of this patent UNITED STATES PATENTS334,450 Mason Jan. 19, 1886 505,380 Barrett Sept. 19, 1893 571,760Guilleaume Nov. 24, 1896 591,997 Bishop Oct. 19, 1897 677,730 Woods July2, 1901 762,033 Ferres June 7, 1904 1,115,265 Weis Oct. 27, 1914-1,263,577 Lochrnan Apr. 23, 1918 2,097,501 Reichelt Nov. 2, 1937 FOREIGNPATENTS 565,344 Great Britain Nov. 7, 1944

3. A METHOD OF INSULATING AN ELECTRIC CONDUCTOR BY APPLYING A STRIP OFPAPER THEREAROUND, COMPRISING SUBJECTING SUBSTANTIALLY THE COMPLETEPAPER STRIP TO A HUMIDIFYING PROCESS TO IMPART A CONTROLLED MOISTURECONTENT THERETO, LONGITUDINALLY FOLDING SAID MOISTENED STRIP OF PAPERAROUND SAID CONDUCTOR, AND HEATING SAID PAPER